It is known in the art relating to serial data link systems to transmit a large amount of information in a single wire. For critical applications, the standard single line data bus commonly used in serial data link systems is not suitable. Therefore, multiple sets of data lines in physically separated locations carrying the same data are used. Many of these systems are protected against corrupt data by using poling, parity checking or other software error checking methods. However, such systems are not protected against an open circuit, short to ground or short to a positive supply of one of the serial data links which can render the system useless.
U.S. Pat. No. 4,819,225 issued Apr. 4, 1989 in the name of Hochstein addresses this problem by providing a multiplexing system having a missing pulse detector to detect fault conditions, such as an open circuit, short to ground or short to a positive supply. Since all three fault conditions after a certain period of time will result in dc conditions at the input of the receiver of the system, the pulse detector detects a fault when the detector does not receive any pulses for a certain period of time. If a fault is detected, the detector transfers the input after that certain time period to the other working channels. However, during that certain time period in which the receiver is waiting for the missing pulses, a large amount of erroneous data may pass through the serial data links and reach the receiver. This condition can cause unpredictable results. Therefore, it is desirable to provide a system that detects a fault condition in real time and automatically corrects the serial data to represent the correct data bit.